Tube or not to tube?

I recently worked in a high end store. The best results we found..is to use a tube preamp with a MOSFET solid state amp. Best of both worlds. Tube preamp tubes last alot longer than tube amp tubes by 3x or so, and they are much cheaper than amp tubes.
If I were you I would buy a nice tube pre..use it with your NAD amp (bipolar I believe). You will be blown away by the musicality-listenability. Then step up your amp to a MOSFET type, you will then be awash in tube-like sound. The bipolar amp will deliver tighter and stronger bass but the MOSFET amp will better duplicate tube like bass and distortion quality. However you want it.

Musicrover..the rogue preamp is a good one. There are many other brands, tube equipment these days is all made pretty well, since they appeal to the highend ($) crowd. We carried conrad johnson..a very good brand. I think one of the best values out there is a Conrad Johnson PV10..used, as they are no longer made. I would focus on looks, remote capability, and try to find a good review on it.
As far as the amp... bipolar amps are usually built to amplify current..they sound powerful, usually at the expense of ultimate warmth/musicality. Your NAD is this type I believe. MOSFET amps usually amplify voltage, which makes them sound more warm/musical at the expense of ultimate bass power performance. MOSFET is similar in this respect to a tube amp.
To illustrate this point..Conrad Johnson makes a solid state amp MF2500 which uses MOSFET input stage and bipolar output stage, this amp reaps the advantages of both types of transistors. This amp sounds awesome..I preferred it to the Krell and Linn amps we sold. Most amps have the input and output stages consisting of the same type of transistor, the MF2500 is rare in this regard.
I read about the NAD 272 and it has input level controls on it! This is perfect for matching it to any tube preamp. I would buy a nice tube pre, connect it to the NAD, adjust the NAD level controls down so the preamp volume knob is turned up as much as possible during listening. This will give you the best dynamic range. Normally, you have to be a little careful when matching different brand preamps and amps because of this issue..but your amp has variable inputs so you're golden.
You can replace your amp with a MOSFET type..this will be more tube like. I believe a single ended MOSFET amp is a class A type...which will sound better than a class A/B type, but total output power will be lower with the class A and will be hot to the touch, warm up your room, and waste power.
We had people return tube amps saying they didn't have enough power (bass) for their needs. If you listen to classical/jazz and have efficient speakers, tube amps will do fine. If you listen to rock/dance and have inefficient speakers solid state amps will do better. System matching can make or break a system.
Hope this helps. Enjoy your adventure!

The jolida stuff is actually wonderful sounding. You will be stunned at the difference compared to NAD. Enjoy the tubeness..many never go back! :)